The couple are both from wealthy backgrounds with Mrs Rausing the daughter of a former Pepsi executive, who owns an island off South Carolina

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Cadogan Place in Chelsea, LondonPhoto: Peter Macdiarmid/Getty Images

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The London home of Hans Kristian and Eva Rausing in Cadogan Place, ChelseaPhoto: JULIAN SIMMONDS

By Sam Marsden, and Duncan Gardham

11:13AM BST 11 Jul 2012

It is thought that the body could have lain undiscovered for several days and up to a week before detectives arrived at the £70 million home on Monday afternoon.

On Monday morning, her husband Hans Kristian Rausing, the heir to the Tetra Pak empire, was arrested while driving erratically in South London.

Despite an apparent overdose, pathologists were unable to find an immediate cause of death due to the state of the body, lending weight to the theory that she may have been dead for some time.

Cadogan Lane: The rear entrance of Eva and Hans Kristian Rausing's property in Cadogan Place (Noble/Draper)

Detectives have seized CCTV footage from cameras on the house in order to find out when Mrs Rausing was last seen alive and are questioning the staff who live in a number of mews houses attached to the five-storey Georgian town house.

A source told the Daily Telegraph: “Whether she had been dead for some time and the last sighting are part of the on-going investigation.”

Mr Rausing, 49, was held in police custody before being taken to a clinic for treatment but sources said it was not believed to relate to any self-inflicted injuries.

He is understood to need a lengthy spell in hospital.

His bail is suspended while he is not in police custody and will restart once he is detained again.

Mrs Rausing's death is being treated as “unexplained”, but it is thought the American born mother-of-four may have died as a result of a drugs overdose.

A post-mortem failed to establish a formal cause of death an d further tests will now be carried out.

Mr Rausing was arrested on suspicion of driving erratically in South London at lunchtime on Monday and was reportedly found to be carrying Class A drugs.

Eva and Hans Kristian Rausing seen in May 2012 (Noble/Draper)

Following the discovery of Mrs Rausing’s body, her husband who had initially been detained for drug possession, was rearrested in connection with her death and held in custody at a South London police station.

After being moved from a police station on Tuesday night, authorities said he was "currently receiving medical attention" at an undisclosed "facility".

Within hours of the discovery of the body, police seized security CCTV footage from inside and outside the property focusing on Cadogan Place and a mews at the rear.

(Getty Images)

The news was reportedly broken to his 86-year-old father Hans Rausing and his wife Marit at their 900-acre East Sussex estate.

Mrs Rausing and her husband have both fought lengthy battles with drug addiction, having first met while attending a rehabilitation clinic in the United States in the early 1990s.

In recent weeks, the couple have been seen out walking in the area. Mr Rausing, looking gaunt and frail, often wore a baseball cap and was photographed carrying rolling tobacco.

In another photograph, he is dressed in a jacket and trousers, and carrying a roll of banknotes in his hand.

His wife has been seen in cut-off trousers and open-toed sandals, carrying a bottle of Eludril mouthwash, which can be used to treat gum disease and bleeding gums.

A spokesman for Scotland Yard said: “On Monday 9 July a 49-year-old man was arrested on suspicion of possession of drugs. Following a subsequent search of an address in Cadogan Place SW1, a body was found.

The London home of Hans Kristian and Eva Rausing in Cadogan Place, Chelsea (Julian Simmonds)

“The death is being treated as unexplained. We believe we know the identity of the deceased but await further confirmation The man was further arrested in connection with the death and is currently in custody at a south London police station.”

Mrs Rausing, who was born Eva Kemeny, is the daughter of a wealthy Pepsi Cola executive .

The Kemeny family live on Hilton Head Island, an idyllic spot off South Carolina known for it's beaches and annual wine tasting festival.

Mrs Rausing's younger sister Be Kemeny, who used to be married to Jack Kidd, the polo playing brother of model Jodie Kidd, lives in a beach house on the island with her children.

In a statement issued on Tuesday night, her parents, Tom and Nancy Kemeny, said that "along with all of their family are deeply saddened by the death of their beloved daughter, Eva Louise Rausing".

They added: "Eva was a devoted wife for twenty years and mother of four much loved and wonderful children.

"During her short lifetime she made a huge philanthropic impact, supporting a large number of charitable causes, not only financially, but using her own personal experiences. She bravely fought her health issues for many years.

"The family is devastated at her death and asks to be given privacy at this difficult time.”

Mr Rausing’s family, who established the Swedish Tetra Pak drinks carton empire, are worth an estimated £4.5 billion and were last year ranked as Britain’s 12th richest in the Sunday Times Rich List.

Mr Rausing and his wife shared their time between London and Barbados, where they own an 11 bedroom beachfront mansion worth £15 million. They have four children.

He moved to Britain in 1980 in order to escape Sweden’s punitive tax laws but is reputed to live modestly, doing his own cooking and driving a Morris Minor car around the local village.

Mr Rausing, who is known to his friends as Hans K to differentiate himself from his father, did not enter the business world and instead travelled to India where it is thought he first experimented with drugs.

After meeting his wife in a clinic in the United States, the pair moved to London and set up home in Chelsea.

Eva Rausing was the daughter of a former Pepsi executive (Rex)

They have both donated millions to charity and have lent their support to several organisations that support people struggling with addiction.

The couple have worked on a number of charitable initiatives with the Prince of Wales, who once described Mr Rausing as “one very special philanthropist”.

A spokesman for the charity Action on Addiction, which has long enjoyed Mrs Rausing's support said: "Everyone involved with Action on Addiction is devastated to hear the news of Eva Rausing’s untimely death.

"Without any desire for public recognition, Eva has, through her wonderfully generous support of this and other charities helped so many people for over 20 years. We offer our deepest sympathy to Eva’s family at this time of great loss."

The couple moved into their five-storey mansion after selling another property nearby for £12.65m six years ago.

Neighbours in the multimillion pound homes in Cadogan Place said they rarely saw the Rausings and sometimes wondered if the house was occupied apart from a Filipino maid.

Elizabeth Caldeira, a housekeeper for an Iranian family, said she when she saw the police arrive at the Rausing property she had believed there had been a break in.

Mr Rausing has two sisters Lisbet and Sigrid, who both live in Holland Park, west London.

Lisbet is a successful historian, while Sigrid is a human-rights activist, who funds a number of charitable foundations.

In a statement his parents, Hans and Märit Rausing, together with their relatives said: "Hans and Märit Rausing and their family are deeply shocked and saddened to hear of the tragic death of their daughter-in-law Eva Louise Rausing.